Electrostatic printing systems generate a latent electrostatic image on a photoconductor member using an optical scanning unit, which includes a rotatable element having a plurality of mirror facets, e.g., a rotating hexagonal mirror. A toner image is developed on the photoconductor member and is transferred, either directly or indirectly, to a medium. The toner is transferred electrostatically to the photoconductor member from a developer unit. Some electrostatic printing systems may use a dry toner powder whereas other printing systems, such as liquid electro-photographic (LEP) printing systems, may use a liquid toner.